The invention relates generally to inspection methods for machined parts and, more particularly, to methods for inspecting an edge break of a part.
Inspection of features of a machined part is desirable to ensure that such features are appropriately configured or shaped to achieve suitable mechanical properties. For example, in parts such as turbine airfoils, compressor fans, blade roots etc., a sharp edge break or a discontinuity may result in a section of the part that may wear out quickly or crack when subjected to thermal and/or mechanical stress. Therefore, it is desirable to obtain an accurate measurement and characterization of such edge breaks.
Typically, edge breaks on the parts are performed by hand benching methods and the measurement and analysis of such edge breaks is through a manual process. In such systems, an image of the target edge break is obtained through a sensor and such image data is analyzed to determine the quality of the edge break. Unfortunately, since orientation of an edge measurement tool is manually performed, undesirable variation in the characterization of the edge breaks may be introduced due to differences in the training and/or skill level of the operator. For example, the variation of the sensor orientation from different operators may result in reduced measurement repeatability and accuracy.
In certain systems, the sensor tip is designed to ensure that the measured target edge break is in the working field of the sensor. Further, if the tilting angle of the sensor is too large, the live display image will be out of focus of the sensor. Such sensor configuration is not able to accurately reduce the error introduced due to the sensor orientation. In certain other systems, projected line based systems are employed to inspect the quality of edge breaks. Typically, a single line is projected onto the edge break and triangulation method is employed to determine the profile of the edge break. However, if the sensor is tilted then the profile is not normal to the edge. Further, the tilt of the sensor causes focus errors that may not be corrected through the single line projection technique.
Accordingly, it would be desirable to develop inspection techniques that accurately characterize an edge break by reducing the error due to the variation in the sensor orientation.